Although their relative rankings changed little from the year before, the NRDC's clean air director John Walke says both states actually reduced their emissions.

"That reflects a 20 percent drop in power plants' toxic pollution in Missouri, and a 16 percent reduction from that sector in Illinois," Walke said. "So those are impressive reductions." About a million pounds less air pollution in each state.

Walke says that’s also good news for our region’s water and fish, which are contaminated with mercury – a power plant pollutant.

“It builds up in water bodies through a process called bioaccumulation, but once you reduce it, you can actually see a pretty substantial recovery.”

Exposure to mercury can cause developmental problems - pregnant women and children are most at risk.